This invention relates generally to a heat exchanger or more explicitly to a recuperator and more particularly to an apparatus and method for assembling the recuperator.
Many application use the recuperator which is a specific type of heat exchanger to extract heat from a fluid. One such application is that of a gas turbine engine. For example, to increase the operation efficiency of the gas turbine engine, heat is extracted from the exhaust gas and used to preheat the intake air. Typically, the recuperator for a gas turbine engine must be capable of operating at temperatures of between about 500 degrees C. and 700 degrees C. and internal pressures of between approximately 450 kPa and 1400 kPa under operating conditions involving repeated starting and stopping cycles.
Many recuperators are of a primary surface construction. In a primary surface recuperator, a plurality of thin sheets are stacked in a spaced apart configuration to form a cell. The cells are assembled, such as by welding, to form a core. The spacing within the core forms a plurality of donor passages and a plurality of recipient passages. In applying the recuperator to the gas turbine engine, the hot exhaust gas is passed through the donor passages and an atmospheric temperature intake air is passed through the recipient passages. Heat from the hot exhaust is transferred through the sheet and absorbed by the cooler intake air increasing the efficiency of the gas turbine engine.
In most applications the primary surface sheet used in forming the cell is very thin, flimsy and difficult to maintain a uniform cross sectional area of the passages between the sheets. To enhance the rigidity of the thin sheets, the sheets are formed into an accordion type configuration forming peaks or crests and valleys forming a plurality of upwardly and downwardly opening, transversely extending, relatively deep grooves being relatively closely spaced and having substantially vertical side walls or fins. In forming the recuperator using such sheets, the peeks of alternate sheets are aligned and the valleys of alternate sheets are aligned to form the donor passages and the recipient passages. Additionally, many of the sheets are formed with a serpentined configuration to enhance a controlled turbulent which increases heat conductivity and resulting efficiency. In manufacturing such recuperators, the component parts are fixedly attached together by a welding process to prevent leakage from the respective donor passages and recipient passage. To insure the integrity of the recuperator, the welding process and technique used is very critical to maintaining a sealed separation between the plurality of donor passages and the plurality of recipient passages.
U.S. Pat. No. 5,060,721 issued on Oct. 29, 1991 to Charles T. Darragh discloses an example of one such recuperator. The recuperator disclosed in this patent has a circular configuration. The recuperator has a plurality of cells made from a pair of primary surface sheets, a plurality of spacer bars and a plurality of guide strips. The component parts are welded together to form the recuperator. The welding of these thin sheet and component parts into a cell having a sealed interface is difficult to accomplish in a cost effective and efficient manner.
After the assembly of the sheets and component parts into the cell and the assembly of the cells into the core, additional component, such as ducts, must be added to the core. The ducts direct the hot exhaust gas to and through the donor passages and direct the intake air to and thorough the recipient passages. These ducts are also welded to the core. The welding of these thin sheets of the core to the ducts and the relative positioning thereof with a sealed interface is difficult to accomplish in a cost effective and efficient manner.
The present invention is directed to overcome one or more of the problems as set forth above.
In one aspect of the invention, a recuperator assembly line is adapted to assemble a core. The core has a plurality of donor passages therein and a plurality of recipient passages. The recuperator assembly line has an assembly station including an upper stacking portion defining a first side and a second side. The upper stacking portion is rotatable between a first position and a second position. The core is positioned in the upper stacking portion. An assembly fixture is positioned at one of the first side and the second side. The assembly fixture has a plate having a bore therein. A plurality of locating members are positioned in one of the assembly fixture and the assembly station. The plurality of locating members define a preestablished relationship between the assembly fixture and the assembly station. A locating mechanism is positioned in the bore, the locating mechanism has a first end having a positioning portion located near said first end. A one of a plurality of ducting structures is attached to the positioning portion of the locating mechanism. The one of the plurality of ducting structures is positioned in a preestablished position relative to one of the plurality of donor passages and the plurality of recipient passages. A welding station has a welding head and forms a weld. A control station has a plurality of sensors, a plurality of switches and a controller operatively receiving an input from the plurality of sensors and the plurality of switches. The controller defines a relative position of the one of the plurality of ducting structures and the core. And, the one of the plurality of ducting structures is attached to the core with the weld.
In another aspect of the invention, a method of assembling a core into a recuperator has the steps of positioning the core in an upper stacking portion; securing the core within the upper stacking portion; positioning one of a plurality of ducting structures within an assembly fixture; positioning the assembly fixture relative to the upper stacking portion in a preestablished relationship; and welding the one of a plurality of ducting structures to the core.
In another aspect of the invention, a circular recuperator assembly line has an assembly station defining an axis and having a core defining an axis xe2x80x9cAxe2x80x9d being aligned about the axis of the assembly station and is removably positioned within the assembly station. An assembly fixture defines an axis and has a ducting structure removably positioned therein relative to the axis of the assembly fixture. The assembly fixture is position in axial alignment with the axis xe2x80x9cAxe2x80x9d of the core. A control station has a controller, a plurality of switches and a plurality of sensors defining an input to the controller of the relative position of the core within the assembly station and the ducting structure relative to the core. A welding station has a welding head and a lead. The welding station is operatively connected to the control station and the assembly station. And, a weld is interposed the core and the ducting structure.